Hot Water Recirculation
I did not want to run cold water down the drain while waiting for hot water. It would take 30 seconds or more to get hot water. So I found an electronic timer/relay, a solenoid valve and a bunch of plumbing fittings and went at it.
Parts List
Timer/relay controller
12v 3/4" Solenoid Valve
2-3/4" pipe couplers
2-3/4" male pipe to barbed fittings to fit your flexible tubing.
1/2" pipe coupler to attach to the hot side of the water manifold. The spot opposite the toilet is usually open
If there are no unused spots you have to T into a PEX hot line.
6 ft of tubing. I used 5/8" to match up with the barbed fitting the hardware store had that day.
1/2" spin weld tank fitting to glue to the water tank
Adhesive for the 1/2" spin weld fitting
1/2" hose pipe to barbed fitting to fit your flexible tubing.
4 hose clamps
Teflon plumbing tape
Wire ties.
12v on/off switch
12v momentary contact switch
This is the timer/relay circuit I used.
Directed Electronics Inc 528T 12v Accessory Pulse Timer
Amazon.com : Directed Electronics Inc 528T 12v Accessory Pulse Timer :... (http://amazon.com/gp/product/B0009WP09K/ref=oh_aui_search_detailpage?ie=UTF8&psc=1)
And the solenoid valve. You might be able to find a 1/2" one.
12V Solenoid Valve - 3/4"
12V Solenoid Valve - 3/4": Industrial Solenoid Valves: Amazon.com: Industrial... (http://amazon.com/gp/product/B007R9U9BM/ref=oh_aui_search_detailpage?ie=UTF8&psc=1)
At each end of the valve you will need a pipe couple and a barbed fitting of the appropriate size for the tubing you are using.
Attaching a fitting to the low density polyethylene water tank is not easy. You cannot use regular solvent glues. The following fitting works well with the 3M adhesive meant for this type of plastics. A barbed fitting for the tubing size you are using is needed here.
Ameri-Kart (53) 0.5" Female Pipe Fitting
Amazon.com: Ameri-Kart (53) 0.5" Female Pipe Fitting: Automotive (http://amazon.com/gp/product/B00FFAW972/ref=oh_aui_search_detailpage?ie=UTF8&psc=1)
3M 4693H Clear Scotch-Weld High Performance Industrial Plastic Adhesive, 5 Ounce
3M 4693H Clear Scotch-Weld High Performance Industrial Plastic Adhesive, 5... (http://amazon.com/gp/product/B007XIMYX8/ref=oh_aui_search_detailpage?ie=UTF8&psc=1)
This is an alternate (and less expensive) way to connect a 1/2" pipe to your tank. The Uniseal fittings are a rubber grommet that fits in a hole you drill in the tank and then you slide the pipe through hole in the grommet. It makes a tight fit with some give for movement. They come in different sizes. I have a larger one to use when I put in a gravity/fast fill port.
1/2'' UNISEAL Flexible Tank Adapter (bulkhead)
1/2'' UNISEAL Flexible Tank Adapter (bulkhead): Pet Care Products: Amazon.com... (http://amazon.com/UNISEAL-Flexible-Tank-Adapter-jbulkhead/dp/B00BD6SXL8/ref=pd_sim_indust_2?ie=UTF8&refRID=1PGE7VBJMBPBXF4TGA0W)
The flexible tubing is much easier to run than PEX. There is not a lot of room around the manifold and PEX is pretty stiff.
From the hot side of the manifold run the flex line to the top of the bay where it connects to the solenoid valve. From the solenoid valve run the flex line to the fresh water tank connection which is slightly lower than the solenoid valve.
I mounted the timer inside the kitchen cabinets so that I could adjust timing if needed. The on/off switch and the momentary switch are mounted on the kitchen cabinet face just under the cooktop.
I have the timer set for 20 seconds. When the momentary switch is pushed the solenoid valve is opened for 20 seconds. Cold water is pumped to the hot water heater tank, hot water comes back towards the manifold, the water between the hot water tank and the manifold that has cooled off is returned to the fresh water tank. After 20 seconds the solenoid valve closes and there is hot water at the manifold. Now there is only 5-10 seconds of cold hot water between the manifold and the kitchen, bathroom or shower.
I thought about using a "T" in the shower hot water line close to the shower valve which would have gotten the hot water to the manifold and to the shower valve but the plumbing runs seemed much more difficult. The bathroom sink and the kitchen are the most commonly used fixtures. A "T" in the kitchen hot water line would work but that involves crawling under the sink to do plumbing and a potential leak. So the manifold was a good choice.
While doing all of this I removed the panel in front of the fresh water tank, cut it into three pieces and added some hinges and a latch. Now I can just open the door to see how much water is in the fresh tank and store a few more things behind the panel.
Roger
Roger - You are way above my pay grade. ;D
Looking forward to seeing it.
That's what I had in mind except I thought of a tee into the line coming out of the bottom of the tank behind the water pump.
You Rick are above my paygrade too. ;D
Excellent post!
Don
Rick, I though about that as well but thinking about that as a return point then you would have to pump against the water in the tank, hard on the pump. I think pumping it back into the top of the tank is easier on the pump and way easier then trying to put a "T" in the PEX lines behind the pump.
Roger
People around here know I work on my own stuff. No one has ever accused me of fixing any of it.
When the pump kicks on wouldn't it be just feeding into the back side of the pump since that line is dual purpose?
I don't remember the formula to figure the difference in pressure to pump a 1/2 " line to the top of the tank vs pushing against surface pressure at a lower level. I wouldn't think it would be significant.
What good problems to have.
I will sleep on that. I sure like your setup.
@Rodger Nice work. I've bookmarked for that day way off in the future when I have some spare time to go at this. :) Thanks for the excellent write up.
see ya
ken
Hi Guys,
I accomplished a hot water saver by using a 12 volt solenoid water valve, some plastic tubing and a timer... to run the "cool" water water back to the fresh tank for a few seconds. This allows the hot water to make it to the sink/shower etc. where the solenoid valve is located.
Jim
Rick, As I understand the plumbing works, the pump pushes fresh water to the cold side of the mainfold and to the hot water tank. A cold demand sends cold water through the cold manifold to the open faucet. A hot water demand sends cold water to the hot water tank displacing hot water towards the hot water manifold and then to the open faucet. It is the water between the hot water tank and the mainifold that has gone cold that we are trying to put back into,the fresh tank rather than down the drain into the gray water holding tank.
Roger
In an effort to save water when extended dry camping in Quartzsite, I found this old thread.
I looked at the RV Aquaview product, but did not want to drill holes in the Corian in the shower, and the thought that having a blue plastic rod with black PVC pipe in the shower just seemed too Winnebago to me. So, I followed Roger's methodology here and plunged into the project and got-er-done.
I used this 12V water valve off Amazon (looks just like the icemaker valve on my fridge) (2 for $10...just in case since they're Chinee), Amazon.com: Ximimark 2Pcs 1/2" Thread Plastic Electric Solenoid Valve Water... (https://www.amazon.com/gp/product/B07KCGYQVD/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1)
and this made in the USA timer: Small Miniature time on off cycling delay relay 0.1 sec to 9999 hours. 5V... (https://www.amazon.com/gp/product/B015Z2EQCU/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1) and programming buttons. Online instructions on how to set it.
I wired the power for the timer/valve to the vanity make up light switch, and as a trigger, installed a momentary on push button switch right next to that below the sink.
I plumbed the system by gaining access to the rear of the shower thru panels in the make up corner cabinet in the bedroom, installed a sharkbite T fitting and several 90's right at the hot water inlet to the shower valve, and ran 1/2" PEX under the rear of the shower, behind the toilet, to under the sink area, where I installed the valve and timer under the left sink drawer, just above the fresh tank fill point and ran the PEX down to the wet bay on the driver's side (total of about 8' of PEX). Had to pick out a ton of silicone and then resealed it all afterwards. Ran the hot water return down into the wet bay and connected it with a sharkbite T and some adapters into the fast fill set up I'd put in last year. Added a check valve in place of the manual on/off valve I had in there for the fast fill. See picture.
I programmed the timer with program #14, "single shot" and set the timer to 25 seconds and that gets warm water to the shower....enough to wet my hair when I jump in. On cold days, I'll just hit the trigger button twice. It's gonna save me a lot of water...guessing a 1/4 to 1/3 tank.
Man I love this forum. Thanks again for all the advice here. Woody
Nice job Woody. This hot water recirculator has served us well for several years now. Susan thought it was the best thing I had come up with until I did the automatic water pump shutoff.
A direct source for the timers as well as brake flashers and other little timing circuits is:
Multi-Functional 3V-18V Time Delay Relay | Timers.shop (http://timers.shop/Multi-Functional-3V-18V-Time-Delay-Relay-Timer-5-amp_p_12.html)
The mini timers are not the easiest thing to program so guess well on time. The adjustable one I used at the time has a knob or screw to adjust the timer. But 20 seconds seems OK. If not we just run it twice.
I also used 5/8" tubing and a 3/4" valve. it lets more water move per second. When we turn ours on the pump runs continuously for 20 seconds.
Nice jobs. I am paranoid about modifying any tanks as they are non replaceable. You guys are good.
As part of our home safety setup for disasters I have a nice water pump in a box and a large 12 volt source and 2 60 gallon water bladders and various length drinking water hoses. So I can pump extra water into the coach if needed when dry camping.
Obviously I am filling the grey tank way more than your way.
White man build big fire, stand far away. Indian build small fire, stand close.
There are lots of ways to save water and energy. This is a good one.
Bob,
I don't know where you got your info but they are still available. A few months ago I checked on a domestic tank they were still about $1500 plus shipping.
Mike
Thanks. That's great
I recently added two temperature gauges, the red on measures water temperature at the AquaHot and the other measures water temperature at the hot water distribution manifold to see how well the hot water recirculator is doing.
This morning this the first picture shows the temperatures when we got up. I ran the recirculator through two cycles (40 seconds) to get to the second picture.
Hot water at the shower or anywhere else in less than 5 seconds compared to a minute or so. If you are trying to conserve water this is a couple gallons or more every time you want hot water from a cold start.
The temperature gauges are powered when the water pump is on and go off when the water pump shuts off automatically.
Water Pump Timer Automatically Switches Pump Off (https://www.foreforums.com/index.php?topic=30564.0)
Dumb question... Does the house water tank heat up also? As this is used.. If so.. how much? approx?
There is no house water tank. The AquaHot tank filled with coolant heats to 180 to 190° depending on heating method. The fresh water in the coils around the tank (in this AquaHot model) heats up to the about that temperature. The AquaHot mixing valve mixes cold water and hot water to deliver 120° water to the manifold.
After 12 hours with no heat added (electric or diesel boiler) and after two showers and dishes the AquaHot tank is still at 148°
Running the water pump for 20 seconds moves about 1 gallon from the hot side of the manifold back to the fresh tank. Depending on the starting temperature at the manifold it can take 20-40 seconds to reach about 120° at the manifold.
David, my recirc timer runs for 25 seconds. Most of that water is cold. Guessing < a quart of warm/hot water goes back into the fresh tank. You couldn't even measure that temperature rise. The grey water tank in my coach sits right next to the fresh tank, so I guarantee the hot water going down the shower drain into the grey tank heats up the adjacent fresh tank a lot more than the recirc water. It's not a consideration IMHO.
Woody.
Ah. another project for the near future. ! thanks for that. lol.
Roger just got a unitseal in the mail a few weeks ago to plumb in a direct fill... guess I will have to plan on a T fitting there.
Last night I fired up the aqua hot to see if the furnace would come on with my new Attwood ac install (it didn't, still troubleshooting that one) and it took about 25 seconds to get hot water and I thought.. gee what a waste of water and gray tank space...
Pyolet... what about the kitchen sink? Guess you would need to wire in a additional circuit for that, yes?
Yes, the kitchen sink would need another valve/circuit. I don't use hot water much except to shower, so went that route to save the most water for my application. The option of pulling off the manibloc hot in line would be the best option if you wanted hot water savings to all fixtures I guess; but then you still gotta purge the cold from the lines between the manibloc and each fixture, using a little more water, but less than having to heat the manibloc from the aqua hot/hot water heater. W.
If I ever get around to it, I'll just go under the bathroom sink, where the is a manual tank fill valve running between the cold water line and the fresh water tank, and add an electrical valve between the hot water line and the fresh water tank.
Close enough to the shower.
Roger can you describe where you installed the temperature sensors at the Aquahot and the distribution manifold please.
The Aquahot sensor fits in behind the panel on the AH where the thermostats are mounted. (There is a panel that comes off above the wiring panel to revel the thermostats.) It is a snug fit, once in place and the cover plat is back on the stay in place.
There is an unused port on the hot side of the manifold where I added a brass T before the new recirculator line. The sensor fits in the T. It measures the temp of the water when it is recirculating but since water is not going by when hot water is used any other time I am probably going to move it to the hot water line coming from the AH into the manifold. That water is usually 115-120° the mixing valve at the AH is set for 120°.
This really lets me see what the AH is doing. For most users most of the time you don't need to leave the 120 on all day or the diesel at all. 2-4 hrs a day for 120 is enough. You have to figure out for yourself what works for you.
I have a Berkey in my coach. I have a nice looking pitcher that I fill while waiting for hot water and put it into the Berkey. No wasted water, and a lot less technical. My system takes about 2 quarts of water to get hot.
Mike
I used 2 aquarium pumps, with a timer, one for the kitchen sink and one for the shower. I teed into the hot water line just before
the valves and returned the water to the cold water line with a check valve. I push the switch a minute before I want to use hot
water and half a cup of water is hot and the shower just needs to clear the water from the shower hose and the bathroom sink
is probably a cup of water. The pump is put in the line between the tee and the check valve.
My temperature senders are located behind the thermostat plate on the Aqua Hot, behind a cover. The other is on the hot water side of the manifold, each needs a ground wire.
I put in a recirculation loop in my water line to the shower. I ran a tee off my hot water line going up the the shower, through a solenoid valve, back to the water fill line to the fresh tank. The solenoid is activated by a momentary switch I mounted on the vanity next to the shower, connected to a timer switch (similar to what Roger linked). When the solenoid is open, hot water is pumped by pressure from the standard water pump through the lines and back into the fresh water tank. I've found that 20 seconds is sufficient to prime the shower line.
This saves probably 40 seconds of running the water in the shower waiting for it to heat up, if you leave the shower mixer valve at its final comfortable warm temperature setting (20 seconds if you turn the mixer full hot). A nice savings if you are boondocking.
I suppose if you were in some really cold setting you could do this periodically for a few minutes to elevate the temperature of the fresh tank and wet bay by a few degrees by cycling the full content of the water heater (in our 295).
Yeah I did something similar going from the Mana block back to my direct fill tank fitting. And I put in everything I needed but I still haven't wired to darn thing yet. I did use a lot of Rogers ideas so thanks for that Roger. I'm really good at doing things on the coach but sometimes not so great at the finishing part. but I'm going to wire it to my old fill switch when I redo my wet Bay once again. since my electric dump valves have seem to crap out and I'm going to go and put manual ones back in it was an experiment and it didn't last as long as I thought it would. I also noticed that waste Master no longer sells the electric valves so they must have been having problems with them that's about $300 I wasted for nothing. Could have bought a lot of beer for for that amount..
I'm gearing up to do this project soon. Quesiton: why use a timer relay and not a latching switch to activate the solenoid? Seems like added complexity that results in less control.
As always, thanks for blazing the way for us new guys ^.^d
As I've been thinking about adding one too, I think the idea is to push once and forget it. With a latching relay, you'd have to remember to turn it off at a certain point as not to recirc your entire fresh supply through the water heater.
I used an adjustable timer so that a single press of a momentary switch starts and ends the process. 20 seconds most of the time is about long enough. I can see what happens on the temperature displays. In cold weather we might run it twice.
You don't need a timer, it is an added convenience. If your water pump is powered through a latching relay that is triggered by a momentary ground (that is what pushing the water pump switch does) an extra pair of Bosch style relays can turn on the water pump when you press the recirculate button if it is not already on. If the pump is on it does nothing.
Your water pump latching relay can also be on a timer so that it shuts off after a period of time you select so that the risk of leaving the pump on (especially if you are away) is zero.
If you are using a city water connection a 12v ball valve can be added to your incoming water supply. If you turn on the pump switch, it opens the valve. If the water pump is on a timer your city water connection also automatically shuts off if you are not using water. Risk reduction.
If you are on a city water connection you need to watch your fresh water tank level since you are not really recirculating water from the tank but adding city water to the system that ends up in the fresh water tank.
All simple stuff to make your water system more efficient and safer.
I finally checked this one off the list. I went all the way to the back of the shower like Woody. There's approximately 18' of half inch pex between the manibloc and shower head which equates to .18 gallons per shower. Not a meaningful amount unless you boondock a lot (which we do).
I opted for a latching switch for simplicity, which I installed under the sink near the water pump switch. When I have more time I'll add a temp gauge like Roger did.
I really like being able to add hot water to the tank to add heat if it was ever needed. Very nice 👍👍
Scott
Elliott did you add the spin weld fitting on your fresh water tank and did you use the 3M adhesive that Roger recommended or did you actually spin weld it to your tank?
I used the 3M adhesive he recommended. The spin welding drill attachment was stupid expensive.
I put a quick fill on our water tank years ago. Cheap, easy, fast and no leaks.
I use it for a filtered fill but it can be used for anything.
Photos are worth any explanation. uniseal fitting water at DuckDuckGo (https://duckduckgo.com/?q=uniseal+fitting+water&t=newext&atb=v325-1&ia=web)
https://www.youtube.com/watch?v=Vv14eNJmUeU
Pierce
Interesting. Pierce, did you have to remove the water tank in order to poke the hole in it? The video shows a small tank, already out, sitting on a nice workbench. Not quite real world for me.
David,
If you have the drill with hole saw ready to go, you can make the hole and install the Uniseal in less than one minute. I was careful not to drop the plastic remaining in the hole saw into the tank. Then, it depends on what kind of fitting you want to push into the Uniseal.
Best to use a felt marker pen to mark where you want to drill the hole, use a small bit to make a pilot hole and then use the hole saw I have included to make the hole. Only takes a second to clean up any plastic debris and then just push the fitting in place.
Here are all the tools I used. This is a 1 out of 1 to 10 in difficulty. I installed the filter housing steel mount on the wall so the pipe into the tank would not move. Probably a good thing to do before you drill the hole in the tank so you can see exactly where the pipe will hit the tank. So, mount the filer bracket, push a plastic pipe into the filter mount and see where it's going to touch the tank and then make the hole. This way, the pipe is perpendicular to the surface of the tank.
No sealer on the Uniseal, just pipe compound on the threads into the filter body. Never even a drop of water anywhere.
The tank fills much faster than the OEM filler but depends on pressure. We drive with the tank low because of all the grades in the Sierras. Once in a campground, I connect and start filling, staying to watch so it does not overflow. Last week, it filled in about 7 minutes as we had good pressure.
No stupid questions, please ask.
Pierce
Pierce, nice tip there with those uniseals! Both hot water recirculation and a top fill are on my list of "to-do's" this year.
Two questions:
What size uniseal and PVC fitting did you use on that top fill/filter assembly?
Any tips on how to minimize plastic chips from getting into the tank as you use the hole saw to cut the opening?
Thanks again! Jeff
Jeff,
It was on the photo but our Forum changed the letters for some reason.
I used a 1 3/4" hole saw and a 1" Uniseal. The 1" size is the I.D. for the size of the pipe that slides in. Since I did this a while ago, check the directions when you get the Uniseal.
I drilled the pilot hole pulling the bit out and cleaning it every couple of seconds. With the hole saw, I also went in a few thousands, cleaned the area and repeated it until it went though. The plastic tank is safe but I didn't want any shavings to clog anything but the undersink filter would catch anything in the drinking water and the sink and shower have never shown anything.
I think I used a small piece of coarse wet or dry on one finger to smooth the edges on the tank before I installed the Uniseal.
You could put a cap on the PVC with a tiny bit of paint to mark the center. Then push it in until it makes contact with the tank and then drill the pilot hole there. Or, a tiny bit of paint all around the PVC spinning it a turn or two when it makes contact and then marking the middle.
My pleasure!
Pierce